Expandable stent and delivery system

ABSTRACT

An expandable stent and delivery system is provided for enhancing luminal dilation of a blood vessel and treating aneurysms. The delivery system includes proximal, intermediate and distal cylindrical members disposed on and spaced apart along an elongated core member such that first and second gaps are formed. The expandable stent includes anchor members which align with the gaps. The expandable stent is mounted on the intermediate cylindrical member, and the anchor members are disposed within the gaps thereby locking the stent onto the core member.

This application claims the benefit of Provisional Application Ser. No.60/412,867 filed Sep. 23, 2002.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to intravascular expandable devices and deliverysystems for implantation within a vessel of the body, and moreparticularly to an expandable stent and delivery system which may beused in the treatment of blood vessel disorders. More specifically, theexpandable stent and delivery system may be used in the treatment ofblood vessel blockage and aneurysms which occur in the brain.

2. Description of the Prior Art

On a worldwide basis, nearly one million balloon angioplasties wereperformed in 1997 to treat vascular disease, including blood vesselsclogged or narrowed by a lesion or stenosis. The objective of thisprocedure is to increase the inner diameter or cross-sectional area ofthe vessel passage, or lumen, through which blood flows.

In an effort to prevent restenosis without requiring surgery, shortflexible cylinders or scaffolds, made of metal or polymers, are oftenplaced into a vessel to maintain or improve blood flow. Referred to asstents, various types of these devices are widely used for reinforcingdiseased blood vessels, for opening occluded blood vessels, and fordefining an internal lumen to relieve pressure in an aneurysm. Stentsallow blood to flow through the vessels at an improved rate whileproviding the desired lumen opening or structural integrity lost by thedamaged vessels. Some stents are expanded to their proper size byinflating a balloon catheter, referred to as “balloon expandable”stents, while others are designed to elastically resist compression in a“self-expanding” manner.

Balloon expandable stents and self-expanding stents are generallydelivered in a cylindrical form, compressed to a smaller diameter andare placed within a vessel using a catheter-based delivery system. Whenpositioned at a desired site within a vessel, these devices are expandedby a balloon, or allowed to “self-expand,” to the desired diameter.

U.S. Pat. No. 4,768,507 entitled, “Intravascular Stent and PercutaneousInsertion Catheter System for the Dilation of an Arterial Stenosis andthe Prevention of Arterial Restenosis” discloses a system used forplacing a coil spring stent into a vessel for the purposes of enhancingluminal dilation, preventing arterial restenosis and preventing vesselblockage resulting from intimal dissection following balloon and othermethods of angioplasty. The coil spring stent is placed into spiralgrooves on an insertion catheter. A back groove of the insertioncatheter contains the most proximal coil of the coil spring stent whichis prevented from springing radially outward by a flange. The coilspring stent is deployed when an outer cylinder is moved proximallyallowing the stent to expand.

Also, U.S. Pat. No. 6,126,684 entitled, “Apparatus and Methods forPlacement and Repositioning of Intraluminal Prostheses” discloses adelivery catheter for a radially compressible tubular prosthesisincluding an elongated shaft slideably received within an elongatedsheath. The prosthesis is carried over the distal end of the shaft whereit is contained in a radially compressed configuration by the sheath.Penetrating stay members on the exterior of the shaft engage theproximal section of the prosthesis allowing the prosthesis to berecaptured prior to full release of the prosthesis.

Another stent and delivery system is disclosed in U.S. Pat. No.6,214,036 entitled, “Stent Which is Easily Recaptured and RepositionedWithin the Body.” This patent discloses a self-expanding stent which maybe used in the treatment of aortic aneurysms. This device includeslongitudinal legs having a flange which attaches to a deliveryapparatus. The stent may be easily recaptured after placement andrepositioned to a new position within the vessel. This patent, assignedto a related company, is subsequently referred to and the disclosuretherein is incorporated and made a part of the subject patentapplication.

U.S. Pat. No. 6,361,558 entitled, “Stent Aneurysm Treatment System andMethod” and assigned to the same assignee as the present applicationdiscloses other stent devices. This patent discloses vasculature stentsof various configurations which may be used as aneurysm covers foroccluding, or partially occluding, aneurysms located at variouspositions along the blood vessels.

SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention, there isprovided an expandable stent and delivery system. The delivery systemincludes an elongated core member having a proximal cylindrical memberdisposed about the core member. An intermediate cylindrical member isdisposed about the core member generally positioned distally from theproximal cylindrical member and spaced apart from the proximalcylindrical member to form a first gap. A distal cylindrical member isdisposed about the core member generally positioned distally from theintermediate cylindrical member and spaced apart from the intermediatecylindrical member to form a second gap.

The expandable stent includes at least one proximal leg which extendsproximally from the proximal end of the stent. The stent also includesat least one distal leg which extends distally from the distal end ofthe stent. The stent further includes at least one anchor memberattached to the proximal leg and at least one anchor member attached tothe distal leg. The anchor members have a longitudinal length less thanthe longitudinal length of the first and second gaps and are inwardlyprojected in a direction toward the longitudinal axis of the stent. Thestent is mounted on the intermediate cylindrical member and positionedsuch that the anchor members interlock within the gaps.

The delivery system further includes a deployment catheter disposedabout the core member such that the deployment catheter constrains theexpandable stent about the intermediate cylindrical member causing theanchor members to be maintained in the gaps and thereby causing thestent to be interlocked onto the core member.

In accordance with another aspect of the present invention, there isprovided an expandable stent and delivery system. The delivery systemincludes an elongated core member with a proximal cylindrical memberdisposed about the core member. A distal cylindrical member is disposedabout the core member generally positioned distally from the proximalcylindrical member and spaced apart from the proximal cylindrical memberto form a gap. The expandable stent includes an anchor member attachedto the stent. The anchor member has a longitudinal length less than orapproximately equal to the longitudinal length of the gap and isinwardly projected in a direction toward the longitudinal axis of thestent. The stent is mounted on at least one cylindrical member andpositioned such that the anchor member interlocks within the gap.

The delivery system further includes a deployment catheter disposedabout the core member such that the deployment catheter constrains theexpandable stent about at least one cylindrical member causing theanchor member to be maintained in the gap and thereby causing the stentto be interlocked onto the core member.

In accordance with a further aspect of the present invention, there isprovided an expandable stent and delivery system. The delivery systemincludes an elongated core member with a plurality of cylindricalmembers disposed about the core member and spaced apart to form aplurality of gaps. The expandable stent includes a plurality of anchormembers attached to the stent. The anchor members have a longitudinallength less than the longitudinal length of the gaps and are inwardlyprojected in a direction toward the longitudinal axis of the stent. Thestent is mounted on at least one cylindrical member and positioned suchthat the anchor members interlock within the gaps.

The delivery system further includes a deployment catheter disposedabout the core member such that the deployment catheter constrains theexpandable stent about at least one cylindrical member causing theanchor members to be maintained in the gaps and thereby causing thestent to be interlocked onto the core member.

In accordance with another aspect of the present invention, theintermediate cylindrical member takes the form of a flexible cylindricalsleeve. The flexible cylindrical sleeve includes reinforcement memberslocated at the ends of the cylindrical sleeve such that thereinforcement members resist deformation of the ends of the cylindricalsleeve.

In accordance with a further aspect of the present invention, theelongated core member is tapered such that the proximal section of thecore member has a diameter which allows the core member to be pushedthrough a blood vessel and the distal section of the core member has adiameter less than the diameter of the proximal section of the coremember.

In accordance with still another aspect of the present invention, theexpandable stent includes two proximal legs extending proximally fromthe proximal end of the stent and two distal legs extending distallyfrom the distal end of the stent. Two anchor members are attached to theproximal legs, and two anchor members are attached to the distal legs.The anchor members have longitudinal lengths less than the longitudinallengths of the gaps and are inwardly projected in a direction toward thelongitudinal axis of the stent.

In accordance with another aspect of the present invention, the proximalcylindrical member and the distal cylindrical member take the form offlexible coils.

In accordance with a further aspect of the present invention, a methodis provided for deploying an expandable stent within a blood vessel toenhance luminal dilation of the blood vessel or to treat an aneurysm.The method includes the step of providing an expandable stent anddelivery system. The expandable stent is mounted on at least onecylindrical member along a core member of the delivery system. The stenthas at least one anchor member which is interlocked within at least onegap along the core member. The gaps are formed by spaces between aplurality of cylindrical members disposed on the core member. Thedelivery system includes a deployment catheter disposed about the stentwhich maintains the stent in a constrained configuration.

The method further includes the step of inserting the expandable stentand delivery system into a blood vessel and positioning the expandablestent adjacent to a blockage area or aneurysm within the vessel. Themethod also includes moving the deployment catheter proximally allowingthe stent to begin expanding within the vessel, then again moving thedeployment catheter proximally allowing the stent to fully deploycausing the vessel to increase in luminal dilation or causing the stentto cover the aneurysm. Finally, the method includes removing thedelivery system from the blood vessel.

In accordance with still another aspect of the present invention, amethod is provided for resheathing an expandable stent onto a deliverysystem within a blood vessel. The method includes the step of providingan expandable stent and delivery system. The expandable stent is mountedon at least one cylindrical member along a core member of the deliverysystem. The stent has at least one anchor member interlocked within atleast one gap along the core member. The gap is formed by spaces betweena plurality of cylindrical members disposed on the core member. Thedelivery system includes a deployment catheter disposed about the stentwhich maintains the stent in a constrained configuration. The methodfurther includes inserting the expandable stent and delivery system intothe vessel. The method also includes moving the deployment catheterproximally allowing the stent to begin expanding within the vessel. Inaddition, the method includes moving the deployment catheter distallywhich forces the stent back onto the cylindrical member of the deliverysystem. Finally, the method includes removing the stent and deliverysystem from the blood vessel or repositioning the stent and deliverysystem within the blood vessel.

These and other aspects of the present invention and the advantagesthereof will be more clearly understood from the foregoing descriptionin drawings of a preferred embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an enlarged partial sectional view of an expandable stent anddelivery system in accordance with the present invention;

FIG. 2 is an enlarged partial sectional view of the delivery system withan intermediate cylindrical member which takes the form of a helicallywound flexible coil;

FIG. 3 is an enlarged partial sectional view of the delivery system withan intermediate cylindrical member which takes the form of a flexiblecylindrical sleeve;

FIG. 4 is an enlarged partial sectional view of the expandable stent anddelivery system disposed within a blood vessel and aligned adjacent tovessel blockage;

FIG. 5 is an enlarged partial sectional view of a deployment cathetermoved proximally with the proximal section of the expandable stentcompressed within the deployment catheter and the distal section of theexpandable stent expanded within the vessel;

FIG. 6 is an enlarged sectional view of the deployment catheter movedproximally with the expandable stent expanded within the vessel;

FIG. 7 is an enlarged sectional view of the stent expanded within thevessel and the delivery system removed from the vessel;

FIG. 8 is an enlarged partial sectional view of the expandable stent anddelivery system disposed within a blood vessel and aligned adjacent toan aneurysm;

FIG. 9 is an enlarged partial sectional view of the a deploymentcatheter moved proximally with the proximal section of the expandablestent constrained within the deployment catheter and the distal sectionof the expandable stent expanded within the vessel;

FIG. 10 is an enlarged sectional view of the deployment catheter movedproximally with the expandable stent expanded within the vessel andcovering the mouth of the aneurysm;

FIG. 11 is an enlarged sectional view of the stent expanded within thevessel and covering the aneurysm;

FIG. 12 is an enlarged sectional view of the stent expanded within thevessel and a microcatheter inserted through the wall of the stent andinto the aneurysm; and,

FIG. 13 is an enlarged sectional view of the stent expanded within thevessel and covering the aneurysm with an embolic coil deployed withinthe aneurysm.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 illustrates an expandable stent 10 and delivery system 12. Thedelivery system 12 includes a deployment catheter 14 which is anelongated tube with a lumen 16. The lumen 16 of the deployment catheter14 has a diameter in the range of 0.010 inches to 0.25 inches with apreferred diameter of approximately 0.021 inches. Preferably, theproximal section 18 of the deployment catheter 14 is formed of a nylonmaterial having a durometer in a range of about 60 D to 75 D. Theproximal section 18 is sufficiently flexible to traverse a blood vessel,but is sufficiently rigid so that it can be pushed distally through ablood vessel. The distal section 22 of the deployment catheter 14 ispreferably formed of a pellethane material having a durometer of between25 D and 55 D with a durometer of 40 D being the preferred durometer.

The delivery system 12 includes a winged hub 24 coupled to the proximalsection 18 of the deployment catheter 14. The winged hub 24 may be madefrom plastic and aids in the insertion of the deployment catheter 14into a blood vessel. The delivery system 12 also includes an elongatedcore member 26 which is a wire preferably made of Nitinol but may alsobe made from other metal alloys or a polymer material. The core member26 is slideably disposed within the lumen 16 of the deployment catheter14. The core member 26 may have a long taper or may have multiple tapersto give the proximal section 28 of the core member 26 a greater diameterthan the distal section 30 of the core member 26. Preferably, thediameter of the proximal section 28 of the core member 26 isapproximately 0.016 inches while the diameter of the distal section 30is about 0.002 inches. The greater diameter of the proximal section 28gives the core member 26 sufficient stiffness to be pushed through thedeployment catheter 14, and the smaller diameter of the distal section30 provides flexibility for the core member 26 to traverse narrow bloodvessels.

The delivery system 12 further includes a proximal cylindrical member 32disposed about the distal section 30 of the core member 26. Preferably,the proximal cylindrical member 32 is a helically wound flexible coilwith an outside diameter of about 0.016 inches. The coil may be made ofa polymer material but the preferred material is metal. An intermediatecylindrical member 34 (located within the stent and not seen in thisfigure) is also disposed about the core member 26 distally from theproximal cylindrical member 32 and spaced apart from the proximalcylindrical member 32. The intermediate cylindrical member 34 may be acylindrical sleeve or a coil with an outside diameter of approximately0.012 inches. The space between the proximal and intermediatecylindrical members 32 and 34 along the core member 26 forms a first gap36. The length of the first gap 36 may range from 0.019 inches to 0.19inches with a preferred length of 0.040 inches.

A distal cylindrical member 38 is also disposed about the core member 26distally from the intermediate cylindrical member 34 and spaced apartfrom the intermediate cylindrical member 34. Preferably, the distalcylindrical member 38 is a helically wound flexible coil with an outsidediameter of about 0.016 inches. The coil may be made of a polymermaterial but the preferred material is metal. The space between theintermediate and distal cylindrical members 34 and 38 along the coremember 26 forms a second gap 40. The length of the second gap 40 mayrange from 0.019 inches to 0.19 inches with a preferred length of 0.040inches. The distal cylindrical member 38 may also be shapeable so thatthe core member 26 may be used as a guidewire. For example, the distalcylindrical member 38 may be slightly angled to permit the core member26 to navigate through the vasculature of the body.

An expandable stent 10 is mounted on the intermediate cylindrical member34. The expandable stent 10 may take on many different patterns orconfigurations. Examples of such stents are disclosed in U.S. PatentApplication, “Intravascular Stent Device” filed Jun. 5, 2002. Thedisclosures in these applications are incorporated herein by reference.The expandable stent 10 is preferably laser cut from a tubular piece ofNitinol and thereafter treated so as to exhibit superelastic propertiesat body temperature. The expandable stent 10 may include proximal anddistal legs 44 and 46 that are attached to the proximal and distal ends48 and 50 of the stent 10 and extend along the longitudinal axis of thestent 10. The expandable stent 10 also includes anchor members 52 whichare either attached to the ends 48 and 50 of the stent 10 or to theproximal and distal legs 44 and 46 of the stent 10. In addition, anchormembers 52 may be positioned at other locations along the stent betweenends 48 and 50. The anchor members 52 may be projections made frompolymer or metallic material which extend generally parallel to thelongitudinal axis the stent 10 and extend downward toward thelongitudinal axis of the stent 10.

Preferably, the anchor members 52 are helically wound flexible coils andmade of a radiopaque material for use during fluoroscopic visualization.As the expandable stent 10 is positioned and mounted on the intermediatecylindrical member 34, the anchor members 52 attached to the proximalend 48 or proximal legs 44 of the stent 10 align with and are disposedwithin the first gap 36. Similarly, the anchor members 52 attached tothe distal legs 46 of the stent 10 align with and are disposed withinthe second gap 40. In this configuration, the expandable stent 10 islocked in place and can be pushed and pulled through the deploymentcatheter 14 without damaging or deforming the stent 10.

It should be understood that the expandable stent 10 of the presentinvention may alternatively be coated with an agent, such as heparin orrapamycin, to prevent stenosis or restenosis of the vessel. Examples ofsuch coatings are disclosed in U.S. Pat. Nos. 5,288,711; 5,516,781;5,563,146 and 5,646,160. The disclosures in these patents areincorporated herein by reference.

FIG. 2 illustrates the delivery system 12 without the expandable stent.The delivery system 12 includes an elongated core member 26 disposedwithin a lumen 16 of the deployment catheter 14. Proximal, intermediateand distal cylindrical members 32, 34 and 38 are disposed about the coremember 26 and spaced apart from each other such that first and secondgaps 36 and 40 are formed. In the embodiment shown in this figure, theintermediate cylindrical member 34 is a helically wound flexible coil.Preferably, the flexible coil is made of a metallic material and has alength approximately equal to the length of the expandable stent 10.When the expandable stent (not shown) is mounted on the intermediatecylindrical member 34, the stent is constrained about the coil by thedeployment catheter 14. In this configuration, the stent and deliverysystem 12 remain sufficiently flexible to traverse tortuous bloodvessels.

FIG. 3, like FIG. 2, illustrates the delivery system 12 without theexpandable stent. However, in the embodiment shown in this figure, theintermediate cylindrical member 34 is a flexible cylindrical sleeve.Preferably, the cylindrical sleeve is made of a polymer material and hasa smooth outer surface. The length of the cylindrical sleeve isapproximately equal to the length of the expandable stent. When theexpandable stent (not shown) with a drug coating is mounted on theintermediate cylindrical member 34, the stent is constrained about thecylindrical sleeve by the deployment catheter 12. In this configuration,the drug coating on the expandable stent is protected from damage causedby friction between the stent and a non-smooth intermediate cylindricalmember 34 and friction between various components of the stent itself.

Reinforcing members 42 may be disposed on the ends of the proximal,intermediate and distal cylindrical members 32, 34 and 38. Thereinforcing members 42 may take the form of rings or disks and may bemade of a polymer or metallic material, but preferably the reinforcingmembers 42 are made of the same material as the cylindrical members 32,34 and 38. The reinforcing members 42 provide support to the ends ofcylindrical members 32, 34 and 38 so that the ends resist deformation.

FIG. 4 illustrates the expandable stent 10 and delivery system 12positioned within a blood vessel 20. The expandable stent 10 is mountedon the intermediate cylindrical member 34 (located within the stent andnot seen in this figure). The anchor members 52 on the proximal end 48of the stent 10 are disposed in the first gap 36, while the anchormembers 52 on the distal end 50 of the stent 10 are disposed in thesecond gap 40. In this position, the stent 10 is locked into place onthe core member 26. The expandable stent 10 is generally aligned with ablockage area 54 of the blood vessel 20.

FIG. 5 illustrates the expandable stent 10 partially deployed within theblood vessel 20. The deployment catheter 14 is moved proximally causingthe anchor members 52 on the distal end 50 of the stent 10 to exit thesecond gap 40 thereby allowing the stent 10 to partially deploy.

FIG. 6 illustrates the expandable stent 10 fully deployed within theblood vessel 20 and the delivery system 12 still within the vessel 20.The deployment catheter 14 is moved proximally causing the anchormembers 52 on the proximal end 48 of the stent 10 to exit the first gap36 thereby allowing the stent 10 to become fully deployed.

FIG. 7 illustrates the expandable stent 10 deployed within the bloodvessel 20 with the delivery system 12 removed from the blood vessel 20.The expanding force of the stent 10 pushes the blockage area 54 radiallyoutward thereby opening the blood vessel 20 for greater blood flow.

FIG. 8 illustrates the expandable stent 10 and delivery system 12positioned within a blood vessel 20 and aligned with an aneurysm 56. Theexpandable stent 10 is mounted on the intermediate cylindrical member 34(located within the stent and not seen in this figure). The anchormembers 52 on the proximal end 48 of the stent 10 are disposed in thefirst gap 36, while the anchor members 52 on the distal end 50 of thestent 10 are disposed in the second gap 40. In this position, the stent10 is locked into place on the core member 26. The expandable stent 10is generally aligned with an aneurysm 56.

FIG. 9 illustrates the expandable stent 10 partially deployed within theblood vessel 20. The deployment catheter 14 is moved proximally causingthe anchor members 52 on the distal end 50 of the stent 10 to exit thesecond gap 40 thereby allowing the stent 10 to partially deploy and tobegin covering the aneurysm 56.

FIG. 10 illustrates the expandable stent 10 fully deployed within theblood vessel 20 and the delivery system 12 still within the vessel 20.The deployment catheter 14 is moved proximally causing the anchormembers 52 on the proximal end 48 of the stent 10 to exit the first gap36 thereby allowing the stent 10 to become fully deployed and cover theaneurysm 56.

FIG. 11 illustrates the expandable stent 10 deployed within the bloodvessel 20 with the delivery system 12 removed from the blood vessel 20.The expanded stent 10 covers the mouth of the aneurysm 56.

FIG. 12 illustrates the expandable stent 10 deployed with the bloodvessel 20 with a microcatheter 58 inserted into the blood vessel 20,through the wall of the stent 10, and into the aneurysm 56. In thisposition, embolic agents and medical devices may be delivered into theaneurysm 56.

FIG. 13 illustrates the expandable stent 10 deployed with the bloodvessel 20 and covering the aneurysm 56. An embolic coil 60 is deployedwithin the aneurysm 56 and is confined within the aneurysm 56 by theexpandable stent 10.

The present invention is useful for positioning an expandable stentwithin a blood vessel to enhance luminal dilation of the vessel or totreat an aneurysm. To deploy the expandable stent, first the stent ismounted about the intermediate cylindrical member along the core member.The anchor members attached to the ends of the stent are aligned withthe first and second gaps which are formed by the proximal,intermediate, and distal cylindrical members. The expandable stent isinterlocked onto the core member while the deployment catheter isdisposed about the stent holding the stent in its constrainedconfiguration. The delivery system is then inserted into the bloodvessel until the stent is aligned with the blockage area or aneurysmwhich is to be treated. Once positioned, the deployment catheter ismoved proximally which allows the distal portion of the stent to beginexpanding and permits the anchor members attached to the distal legs ofthe stent to become released from the second gap. During expansion, thedistal portion of the stent comes in contact with the wall of the bloodvessel. The deployment catheter is again moved proximally until theproximal portion of the stent expands and allows the anchor membersattached to the proximal legs of the stent to become released from thefirst gap. The stent is now fully deployed and the delivery system maybe withdrawn from the blood vessel.

The present invention is also useful in resheathing the expandable stentduring the deployment process. Here, the stent is positioned on the coremember as described above. Once the delivery system is positioned withinthe blood vessel at the blockage area or aneurysm to be treated, thedeployment catheter is moved proximally to allow the distal portion ofthe stent to expand. If the deployment catheter is not moved proximallybeyond the anchor members attached to the proximal legs of the stent,then the stent remains interlocked on the core wire. In thisconfiguration, the stent can be resheathed and deployed at a differentlocation within the blood vessel. To do this, the deployment catheter ismoved distally forcing the stent back onto the intermediate cylindricalmember and positioning the anchor members attached to the distal legs ofthe stent to become interlocked within the second gap. In thisconfiguration, the expandable stent and delivery system may be withdrawnor repositioned within the blood vessel.

A novel system has been disclosed in which an expandable stent ispositioned within a blood vessel. Although a preferred embodiment of theinvention has been described, it is to be understood that variousmodifications may be made by those skilled in the art without departingfrom the scope of the claims which follow.

1. An expandable stent and delivery system comprising: an elongated coremember having proximal and distal sections; a proximal cylindricalmember disposed about the distal section of said core member; anintermediate cylindrical member disposed about the distal section ofsaid core member and generally positioned on said core member distallyfrom said proximal cylindrical member and spaced apart from saidproximal cylindrical member to form a first gap having a longitudinallength, said intermediate cylindrical member takes the form of aflexible cylindrical sleeve having proximal and distal ends; a distalcylindrical member disposed about the distal section of said core memberand generally positioned on said core member distally from saidintermediate cylindrical member and spaced apart from said intermediatecylindrical member to form a second gap having a longitudinal length; anexpandable stent having proximal and distal ends and a longitudinalaxis, said stent including at least one proximal leg taking the form ofan elongated projection and extending proximally from the proximal endof said stent, said stent also including at least one distal leg takingthe form of an elongated projection extending distally from the distalend of said stent, said stent further including at least one anchormember attached to said proximal leg and taking the form of an extensionhaving a longitudinal length less than the longitudinal length of saidfirst gap and inwardly projected in a direction toward the longitudinalaxis of said stent, said stent also including at least one anchor memberattached to said distal leg and taking the form of an extension having alongitudinal length less than the longitudinal length of said second gapand inwardly projected in a direction toward the longitudinal axis ofsaid stent, said stent mounted on said intermediate cylindrical memberand positioned such that said anchor members interlock within said gaps;a deployment catheter having a lumen extending therethrough and disposedabout said core member such that said deployment catheter constrainssaid expandable stent about said intermediate cylindrical member causingsaid anchor members to be maintained in said gaps and thereby causingsaid stent to be interlocked onto said core member; and, said flexiblecylindrical sleeve includes reinforcement members taking the form ofrings and located at the proximal and distal ends of said cylindricalsleeve such that said reinforcement members resist deformation of theproximal and distal ends of said cylindrical sleeve.
 2. An expandablestent and delivery system comprising: an elongated core member havingproximal and distal sections; a proximal cylindrical member disposedabout the distal section of said core member; an intermediatecylindrical member disposed about the distal section of said core memberand generally positioned on said core member distally from said proximalcylindrical member and spaced apart from said proximal cylindricalmember to form a first gap having a longitudinal length; a distalcylindrical member disposed about the distal section of said core memberand generally positioned on said core member distally from saidintermediate cylindrical member and spaced apart from said intermediatecylindrical member to form a second gap having a longitudinal length; anexpandable stent having proximal and distal ends and a longitudinalaxis, said stent including at least one proximal leg taking the form ofan elongated projection and extending proximally from the proximal endof said stent, said stent also including at least one distal leg takingthe form of an elongated projection extending distally from the distalend of said stent, said stent further including at least one anchormember attached to said proximal leg and taking the form of an extensionhaving a longitudinal length less than the longitudinal length of saidfirst gap and inwardly projected in a direction toward the longitudinalaxis of said stent, said stent also including at least one anchor memberattached to said distal leg and taking the form of an extension having alongitudinal length less than the longitudinal length of said second gapand inwardly projected in a direction toward the longitudinal axis ofsaid stent, said stent mounted on said intermediate cylindrical memberand positioned such that said anchor members interlock within said gaps;a deployment catheter having a lumen extending therethrough and disposedabout said core member such that said deployment catheter constrainssaid expandable stent about said intermediate cylindrical member causingsaid anchor members to be maintained in said gaps and thereby causingsaid stent to be interlocked onto said core member; and, said elongatedcore member is tapered such that the proximal section of said coremember has a diameter which allows said core member to be pushed througha blood vessel and the distal section of said core member has a diameterless than the diameter of the proximal section of said core member. 3.An expandable stent and delivery system comprising: an elongated coremember having proximal and distal sections; a proximal cylindricalmember disposed about the distal section of said core member; anintermediate cylindrical member disposed about the distal section ofsaid core member and generally positioned on said core member distallyfrom said proximal cylindrical member and spaced apart from saidproximal cylindrical member to form a first gap having a longitudinallength; a distal cylindrical member disposed about the distal section ofsaid core member and generally positioned on said core member distallyfrom said intermediate cylindrical member and spaced apart from saidintermediate cylindrical member to form a second gap having alongitudinal length; an expandable stent having proximal and distal endsand a longitudinal axis, said stent including at least one proximal legtaking the form of an elongated projection and extending proximally fromthe proximal end of said stent, said stent also including at least onedistal leg taking the form of an elongated projection extending distallyfrom the distal end of said stent, said stent further including at leastone anchor member attached to said proximal leg and taking the form ofan extension having a longitudinal length less than the longitudinallength of said first gap and inwardly projected in a direction towardthe longitudinal axis of said stent, said stent also including at leastone anchor member attached to said distal leg and taking the form of anextension having a longitudinal length less than the longitudinal lengthof said second gap and inwardly projected in a direction toward thelongitudinal axis of said stent, said stent mounted on said intermediatecylindrical member and positioned such that said anchor membersinterlock within said gaps; a deployment catheter having a lumenextending therethrough and disposed about said core member such thatsaid deployment catheter constrains said expandable stent about saidintermediate cylindrical member causing said anchor members to bemaintained in said gaps and thereby causing said stent to be interlockedonto said core member; and, said proximal cylindrical member takes theform of a flexible coil.
 4. An expandable stent and delivery systemcomprising: an elongated core member having proximal and distalsections; a proximal cylindrical member disposed about the distalsection of said core member; an intermediate cylindrical member disposedabout the distal section of said core member and generally positioned onsaid core member distally from said proximal cylindrical member andspaced apart from said proximal cylindrical member to form a first gaphaving a longitudinal length; a distal cylindrical member disposed aboutthe distal section of said core member and generally positioned on saidcore member distally from said intermediate cylindrical member andspaced apart from said intermediate cylindrical member to form a secondgap having a longitudinal length; an expandable stent having proximaland distal ends and a longitudinal axis, said stent including at leastone proximal leg taking the form of an elongated projection andextending proximally from the proximal end of said stent, said stentalso including at least one distal leg taking the form of an elongatedprojection extending distally from the distal end of said stent, saidstent further including at least one anchor member attached to saidproximal leg and taking the form of an extension having a longitudinallength less than the longitudinal length of said first gap and inwardlyprojected in a direction toward the longitudinal axis of said stent,said stent also including at least one anchor member attached to saiddistal leg and taking the form of an extension having a longitudinallength less than the longitudinal length of said second gap and inwardlyprojected in a direction toward the longitudinal axis of said stent,said stent mounted on said intermediate cylindrical member andpositioned such that said anchor members interlock within said gaps; adeployment catheter having a lumen extending therethrough and disposedabout said core member such that said deployment catheter constrainssaid expandable stent about said intermediate cylindrical member causingsaid anchor members to be maintained in said gaps and thereby causingsaid stent to be interlocked onto said core member; and, said distalcylindrical member takes the form of a flexible coil.
 5. An expandablestent and delivery system comprising: an elongated core member havingproximal and distal sections; a proximal cylindrical member disposedabout the distal section of said core member; a distal cylindricalmember disposed about the distal section of said core member andgenerally positioned on said core member distally from said proximalcylindrical member and spaced apart from said proximal cylindricalmember to form a gap having a longitudinal length, wherein at least onecylindrical member takes the form of a flexible cylindrical sleevehaving proximal and distal ends; an expandable stent having alongitudinal axis, said stent including an anchor member attached tosaid stent and taking the form of an extension having a longitudinallength less than the longitudinal length of said gap and inwardlyprojected in a direction toward the longitudinal axis of said stent,said stent mounted on at least one cylindrical member and positionedsuch that said anchor member interlocks within said gap; a deploymentcatheter having a lumen extending therethrough and disposed about saidcore member such that said deployment catheter constrains saidexpandable stent about at least one cylindrical member causing saidanchor member to be maintained in said gap and thereby causing saidstent to be interlocked onto said core member; and, at least oneflexible cylindrical sleeve includes reinforcement members taking theform of rings and located at the proximal and distal ends of saidcylindrical sleeve such that said reinforcement members resistdeformation of the proximal and distal ends of said cylindrical sleeve.6. An expandable stent and delivery system comprising: an elongated coremember having proximal and distal sections; a proximal cylindricalmember disposed about the distal section of said core member; a distalcylindrical member disposed about the distal section of said core memberand generally positioned on said core member distally from said proximalcylindrical member and spaced apart from said proximal cylindricalmember to form a gap having a longitudinal length; an expandable stenthaving a longitudinal axis, said stent including an anchor memberattached to said stent and taking the form of an extension having alongitudinal length less than the longitudinal length of said gap andinwardly projected in a direction toward the longitudinal axis of saidstent, said stent mounted on at least one cylindrical member andpositioned such that said anchor member interlocks within said gap; adeployment catheter having a lumen extending therethrough and disposedabout said core member such that said deployment catheter constrainssaid expandable stent about at least one cylindrical member causing saidanchor member to be maintained in said gap and thereby causing saidstent to be interlocked onto said core member; and, said elongated coremember is tapered such that the proximal section of said core member hasa diameter which allows said core member to be pushed through a bloodvessel and the distal section of said core member has a diameter lessthan the diameter of the proximal section of said core member.
 7. Anexpandable stent and delivery system comprising: an elongated coremember having proximal and distal sections; a proximal cylindricalmember disposed about the distal section of said core member; a distalcylindrical member disposed about the distal section of said core memberand generally positioned on said core member distally from said proximalcylindrical member and spaced apart from said proximal cylindricalmember to form a gap having a longitudinal length, at least onecylindrical member takes the form of a flexible cylindrical sleevehaving proximal and distal ends; an expandable stent having alongitudinal axis, said stent including an anchor member attached tosaid stent and taking the form of an extension having a longitudinallength approximately equal to the longitudinal length of said gap andinwardly projected in a direction toward the longitudinal axis of saidstent, said stent mounted on at least one cylindrical member andpositioned such that said anchor member interlocks within said gap; adeployment catheter having a lumen extending therethrough and disposedabout said core member such that said deployment catheter constrainssaid expandable stent about at least one cylindrical member causing saidanchor member to be maintained in said gap and thereby causing saidstent to be interlocked onto said core member; and, at least oneflexible cylindrical sleeve includes reinforcement members taking theform of rings and located at the proximal and distal ends of saidcylindrical sleeve such that said reinforcement members resistdeformation of the proximal and distal ends of said cylindrical sleeve.8. An expandable stent and delivery system comprising: an elongated coremember having proximal and distal sections; a proximal cylindricalmember disposed about the distal section of said core member; a distalcylindrical member disposed about the distal section of said core memberand generally positioned on said core member distally from said proximalcylindrical member and spaced apart from said proximal cylindricalmember to form a gap having a longitudinal length; an expandable stenthaving a longitudinal axis, said stent including an anchor memberattached to said stent and taking the form of an extension having alongitudinal length approximately equal to the longitudinal length ofsaid gap and inwardly projected in a direction toward the longitudinalaxis of said stent, said stent mounted on at least one cylindricalmember and positioned such that said anchor member interlocks withinsaid gap; a deployment catheter having a lumen extending therethroughand disposed about said core member such that said deployment catheterconstrains said expandable stent about at least one cylindrical membercausing said anchor member to be maintained in said gap and therebycausing said stent to be interlocked onto said core member; and, saidelongated core member is tapered such that the proximal section of saidcore member has a diameter which allows said core member to be pushedthrough a blood vessel and the distal section of said core member has adiameter less than the diameter of the proximal section of said coremember.